1. Field of the Invention
The present invention relates to a sheet shutter which can be installed in an entrance and a partition portion of a building, such as a factory and a warehouse, and which can be installed in various apparatuses.
2. Description of the Related Art
Conventionally, a sheet shutter is widely known which is installed in an entrance and a partition portion of a building, such as a factory or a warehouse, and in which a sheet provided to be able to be wound and unwound around a sheet drum is lifted and lowered along support posts provided on both sides of the sheet. In such a sheet shutter, there is known a sheet shutter in which a vertically directed rail groove whose left and right inner side is opened is formed in an outer rail formed in each of left and right support posts, in which an inner rail is provided in the rail groove, and an engagement guide engaging with each of left and right end portions of a sheet in a vertically slidable and guidable manner and in a laterally movable manner is formed in the inner rail, and in which an urging member for elastically urging the inner rail toward the left and right outer side is provided between the groove side surface that is one of the front and rear surfaces in the rail groove, and the inner rail, so as to stretch the sheet while elastically pulling the inner rail in the outer direction (see, for example, Japanese Patent Publication No. 6-31502).
In the sheet shutter described in Japanese Patent Publication No. 6-31502, when the sheet receives a strong wind or when a person or an object collides with the sheet, the left and right end portion of the sheet can be effectively prevented from coming off from the engagement guide, because the inner rail is operated to be moved toward the left and right inner side against the elastic force of the urging member so as to reduce the shock caused by the wind or the collision.
However, since the urging member formed by a rectangular parallelepiped block-shaped elastic member is inserted in a filled state between the groove side surface and the inner rail, there is a case where, when the inner rail is moved in the left and right direction, the urging member is compressed and deformed so as to be strongly brought into contact with the groove side surface, and thereby a large frictional resistance is generated so as to prevent the inner rail from being smoothly moved in the left and right direction.
Further, the above-described urging member is generally manufactured by processing a sponge made of rubber or a synthetic resin material into a block shape, and has a disadvantage that it wears due to the reciprocating movement, and that, because of its poor weather resistance, it is deteriorated at an early stage so as to lose the elasticity for stretching the sheet. Further, there is a problem that, when the urging member becomes brittle, a small fragment broken off from the urging member enters the gap between the side wall and the rail base so as to reduce the mobility of the inner rail.
A sheet shutter according to the present invention is configured such that an outer rail having a rail groove is provided in each of left and right support posts, such that an inner rail is accommodated and supported in each of the pair of left and right rail grooves so as to be movable in the left and right direction, such that an engagement guide for vertically movably guiding each of left and right end sides of an unwound sheet is provided in each of the left and right inner rails, and such that an urging member which urges the engagement guide toward the left and right outer side to prevent the sheet from slackening is provided in each of the rail grooves. An object of the present invention is to allow the engagement guide to be smoothly moved in the left and right direction and also to suppress the wear of the urging member.